Pyrimidylalkylthio benzimidazole compounds, pharmaceutical compositions and use

ABSTRACT

This invention relates to 2- and 4-pyrimidinylmethylsulphinyl(and thio)benzimidazoles in which the pyrimidyl group is substituted by an optionally substituted amino group. These compounds inhibit exogenously and endogenously stimulated gastric acid secretion.

This is a divisional of application Ser. No. 829,366 filed Feb. 14,1986, now U.S. Pat. No. 4,777,172.

The present invention relates to novel substituted benzimidazolederivatives, intermediates useful in their preparation, pharmaceuticalcompositions containing them and a method of inhibiting gastric acidsecretion by administering them.

Substituted benzimidazole derivatives that are capable of inhibitinggastric acid secretion are known in the art. For example, GB No. 1500043and GB No. 1525958 disclose a series of 2-pyridylalkyltiio- and2-pyridylalkylsulphinyl benzimidazoles in which the pyridyl group isoptionally mono-substituted by an alkyl or a halogen group. Further, EPNos. 5129B, 74341A and 80602A disclose series of2-pyridylalkylsulphinyl- and 2-pyridylalkylthio-benzimidazoles in whichthe pyridyl group is optionally substituted by 1 to 3 substituentsselected from methyl, ethyl, methoxy, ethoxy, methoxyethoxy orethoxyethoxy; and GB No. 2134523A discloses further such compounds inwhich the pyridyl group is optionally substituted by 1 to 3 groups. Suchcompounds are believed to exert their effects by inhibition of thegastro-intestinal H⁺ -K⁺ ATPase enzyme. (Fellenius E., Berglindh T.,Sachs G., Olke L., Elander B., Sjostrand S. E. and Wallmark B., 1981,Nature, 290, 159-61).

In addition, U.S. Pat. No. 4,359,465 discloses the cytoprotective actionof certain 2-pyridylalkylthio- and2-pyridylalkylsulphinyl-benzimidazoles and their use in the treatment orprevention of gastro-intestinal inflammatory disease.

It has now been found that 2- or 4-pyrimidylalkylsulphinyl (and thio)benzimidazoles in which the pyrimidyl group is substituted by anoptionally substituted amino group inhibit exogenously and endogenouslystimulated gastric acid secretion.

The present invention therefore provides, in a first aspect, a compoundof structure (I) ##STR1## in which, R¹ to R⁴ are the same or differentand are each hydrogen, C₁₋₆ alkyl, halogen, trifluoromethyl, C₁₋₆alkoxy, C₁₋₆ alkanoyl, C₁₋₆ alkoxycarbonyl, RCF₂ O, an ethoxy groupsubstituted by 3 to 5 fluorine atoms, or R² and R³ together form a group--O(CR₂)_(m) O-- where m is 1 or 2, and each group R is hydrogen orfluorine;

n is 0 or 1;

R⁵ and R⁶ are the same or different and are each hydrogen, C₁₋₆ alkyl orC₃₋₆ cycloalkyl, or R⁵ and R⁶ together with the nitrogen atom to whichthey are attached form an azetidino, pyrrolidino, piperidino,piperazino, N-C₁₋₄ alkylpiperazino or morpholino group; and

one of X and Y is a nitrogen atom, and the other is a group CR⁷ where R⁷is hydrogen, C₁₋₆ alkyl or NH₂ ;

or a pharmaceutically acceptable salt thereof.

Suitably, R¹ to R⁴ are all hydrogen. More suitably, R¹ and R⁴ arehydrogen, one of R² and R³ is hydrogen and the other is halogen,trifluoromethyl, RCF₂ O, an ethoxy group substituted by 3 to 5 fluorineatoms, C₁₋₆ alkoxycarbonyl or C₁₋₆ alkanoyl. Preferably, R¹ and R⁴ arehydrogen, one of R² and R³ is hydrogen, and the other is C₁₋₆ alkyl orC₁₋₆ alkoxy; or R¹ and R⁴ are hydrogen and R² and R³ are the same ordifferent and are each C₁₋₆ alkyl or C₁₋₆ alkoxy or together form agroup --O(CR₂)_(m) O--.

Suitably, ethoxy groups substituted by 3 to 5 fluorine atoms are,2,2,2-trifluoroethoxy, 1,1,2-trifluoroethoxy, 1,2,2-trifluoroethoxy,1,1,2,2-tetrafluoroethoxy, 1,2,2,2-tetrafluoroethoxy, andperfluoroethoxy.

Suitably, groups --O(CR₂)_(m) O-- in which m is 1 are for example,difluoromethylene dioxy (--OCF₂ O--); preferably methylenedioxy (--OCH₂O--); suitably, groups --O(CR₂)_(m) O-- in which m is 2 areethylenedioxy (--OCH₂ CH₂ O--) and trifluoroethylenedioxy (--OCHFCF₂O--).

Suitably n is 0. Preferably n is 1.

Suitably one of R⁵ and R⁶ is hydrogen and the other is C₃₋₆ cycloalkyl.Preferably R⁵ and R⁶ are the same or different and are each hydrogen orC₁₋₆ alkyl.

Suitably R⁵ and R⁶ together with the nitrogen atom to which they areattached form an azetidino group. Preferably, R⁵ and R⁶ together withthe nitrogen atom to which they are attached form a morpholino,pyrrolidino, piperazino, NC₁₋₄ alkylpiperazino or piperidino group.

Suitably R⁷ is NH₂. Preferably R⁷ is hydrogen or C₁₋₆ alkyl.

C₁₋₆ Alkyl groups alone or as part of another group (for example C₁₋₆alkoxy, C₁₋₆ alkoxycarbonyl or C₁₋₆ alkanoyl), can be straight orbranched, for example methyl, ethyl, n-propyl, i-propyl, i-butyl,s-butyl, n-butyl, n-pentyl, i-pentyl or n-hexyl. Preferably C₁₋₆ alkylgroups are methyl or ethyl.

Preferably, C₁₋₆ alkoxy groups are methoxy or ethoxy.

Preferably C₁₋₆ alkoxycarbonyl groups are methoxycarbonyl orethoxycarbonyl.

Preferably C₁₋₆ alkanoyl groups are methanoyl or ethanoyl.

C₃₋₆ Cycloalkyl groups are cyclopropyl, cyclobutyl, cyclopentyl andcyclohexyl. Preferably, C₃₋₆ cycloalkyl groups are cyclopentyl orcyclohexyl.

Examples of compounds of the present invention include,

(i) compounds of structure (I) in which X is nitrogen, Y is CR⁷ and n is1, for example,

5-methoxy-2-(4-piperidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(4-morpholino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(4-pyrrolidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(4-dimethylamino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(4-piperidino-5-methyl-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(4-piperidino-5-amino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(4-dimethylamino-5-methyl-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(4-dimethylamino-5-amino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole;

(ii) compounds of structure (I) in which X is CR⁷, Y is nitrogen and nis 1, for example,

5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(5-methyl-6-pyrrolidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(5-methyl-6-morpholino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(5-methyl-6-dimethylamino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(6-piperidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(6-pyrrolidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

5-methoxy-2-(6-dimethylamino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole;and (iii) the corresponding thioethers of the foregoing compounds, iethe analogous compounds in which n is 0.

Compounds of structure (I) in which n is 0, can form pharmaceuticallyacceptable acid addition salts with suitable organic and inorganicacids, the nature of which will be apparent to persons skilled in theart. For example, pharmaceutically acceptable salts can be formed byreaction with hydrochloric, sulphuric, sulphonic or phosphonic acids;aliphatic, alicyclic, aromatic or heterocyclic carboxyl or sulphonicacids; methionine, tryptophan, lysine or arginine and the like.

Compounds of structure (I) in which n is 1 can also formpharmaceutically acceptable acid addition salts, but in aqueous solutionthe salts are less stable than those formed with the compounds ofstructure (I) in which n is 0.

Compounds of structure (I) in which n is 1 can form basic salts byreaction with an appropriate base. Such salts include, for example thesodium, potassium, lithium, calcium and magnesium salts, which can beprepared by methods well known to those skilled in the art; for example,the sodium, potassium and lithium salts can be prepared by reaction withsodium, potassium or lithium hydroxide in an aqueous or non-aqueousmedium, and the calcium salts can be prepared by reaction of the sodium,lithium or potassium salts with calcium chloride in an aqueous ornon-aqueous medium.

Compounds of structure (I) in which n is 0 can also form basic salts butless readily than the compounds of structure (I) in which n is 1.

Compounds of structure (I) in which n is 1 have an asymmetric centre atthe S atom and are thus optically active compounds. As such, thesecompounds exist as two optical isomers (enantiomers). In addition,compounds of structure (I) in which one or more of R¹ to R⁸ is abranched C₃₋₆ alkyl group (either alone or as part of another group) maycontain an additional asymmetic centre(s) due to the presence of theC₃₋₆ alkyl group(s). Again, such compounds will exist as two (or more)optical isomers.

Both the pure enantiomers, racemic mixtures (50% of each enantiomer) andunequal mixtures ofthe two are included within the scope of the presentinvention. Further, all diasteriomeric forms possible (pure enantiomersand mixtures thereof) are within the scope of the invention.

It should be noted that for all the compounds of the present invention,the substituents R¹ and R⁴ as well as R² and R³ are considered to beequivalent at room temperature in solution. This is due to thetautomerism of the benzimidazole nucleus causing an equilibrium betweenthe 2 possible forms.

Processes for the preparation of compounds of structure (I) andpharmaceutically acceptable salts thereof comprise

(a) reacting a compound of structure (II) ##STR2## with a compound ofstructure (III) ##STR3## in which R¹ to R⁶, X and Y are as described forstructure (I) and one of L¹ and L² is SH and the other is a leavinggroup displaceable by a mercaptan;

(b) reacting a compound of structure (IV) ##STR4## in which R¹ to R⁴ areas described for structure (I), with a compound of structure (V)##STR5## in which R⁵, R⁶, X and Y are as described for structure (I), X¹is CO₂ H or CSX² and X² is halogen or C₁₋₄ alkoxy;

(c) reacting a compound of structure (VI) ##STR6## in which R¹ to R⁴ areas described for structure (I), R⁹ is hydrogen or a protecting group andM is an alkali metal atom, with a compound of structure (VII) ##STR7##in which R⁵, R⁶, X and Y are as described for structure (I) and Z is aleaving group;

(d) reacting a compound of structure (VIII) ##STR8## in which R¹ to R⁴are as described for structure (I), R⁹ is hydrogen or a protecting groupand Y is a leaving group, with a compound of structure (IX) ##STR9## inwhich R⁵, R⁶, X and Y are as described for structure (I) and M' is analkali metal atom or the equivalent of an alkali metal atom,

and, optionally, where desired:

(i) oxidising a compound of structure (I) so formed in which n is 0 to acompound of structure (I) in which n is 1;

(ii) reducing a compound of structure (I) so formed in which n is 1 to acompound of structure (I) in which n is 0;

(iii) removing any protecting group R⁹ ;

(iv) forming a pharmaceutically acceptable salt.

Suitable leaving groups L¹ displaceable by mercaptan include halogen,for example chloro, bromo or iodo, arylsulphonyloxy for exampletoluenesulphonyloxy, alkylsulphonyloxy for example methanesulphonyloxy,alkylmercapto, for example methylmercapto, alkylsulphinyl, for examplemethylsulphinyl, or alkylsulphonyl for example methylsulphonyl.

Suitable leaving groups L² are as described for L¹, and may also be C₁₋₄acyloxy, for example acetoxy, or hydroxy.

Suitable alkali metal atoms M include, for example lithium, sodium orpotassium.

Suitable leaving groups Z include, for example, halogen (preferablychloro) and hydroxy activated by esterification with, for example, anaryl or alkane sulphonic acid. Suitable sulphonic acids will be apparentto those skilled in the art, for example p-toluenesulphonic acid ormethanesulphonic acid.

Suitable leaving groups Y are those groups which form a reactivesulphinic acid derivative together with the sulphinyl group to which itis attached, and include for example, C₁₋₄ alkoxy, di-C₁₋₄ alkylaminoand C₁₋₄ alkylmercapto.

Suitable groups M' which are equivalent to a metal atom include, forexample, alkali earth metal atoms, (for example magnesium) which aresubstituted by a halogen atom (for example, bromine).

Suitable protecting groups R⁹ are those conventional in the art forexample as described in "Protective Groups in Organic Synthesis" T. W.Greene 1981 (Wiley). It will be appreciated that the group R⁹ should notbe cleavable under the conditions of reaction of compounds of structure(VIII) and (IX). Such groups include for example benzyl or tritylgroups.

The reaction between compounds of structure (II) in which L¹ is SH andcompounds of structure (III) in which L² is a leaving group can becarried out under basic conditions in the presence of an inert solventat a temperature between ambient and the reflux temperature of thesolvent.

Suitable solvents include lower alkanols, for example methanol orethanol, mixtures of lower alkanols with water, or ethers, for exampledimethoxyethane or tehrahydrofuran.

Suitable bases will be apparent to those skilled in the art and includefor example, alkali metal hydroxides, for example, sodium or potassiumhydroxide, alkali metal alkoxides, for example potassium t-butoxide,alkali metal hydrides, for example sodium or potassium hydride, ororganic tertiary amines, for example triethylamine.

Preferably the reaction is carried out at ambient temperature in ethanolas solvent, in the presence of sodium hydroxide solution.

It is to be noted, and will be apparent to persons skilled in the artthat under basic conditions L² should be a group other than hydroxy oracetoxy, for example halogen, preferably chlorine.

Further, the reaction can be carried out under neutral conditions in thepresence of an inert solvent at the reflux temperature of the solvent.Suitable solvents include those hereinbefore described.

Alternatively, when L² is hydroxy or C₁₋₄ acyloxy, for example acetoxy,the reaction can be carried out under acidic conditions. Suitable acidicconditions will be well known to those skilled in the art, for example,under reflux in hydrobromic acid, optionally in the presence of aceticacid.

The reaction between compounds of structure (II) in which L¹ is aleaving group and compounds of structure (III) in which L² is SH can becarried out under basic conditions as described for the reaction betweencompounds of structure (II) in which L¹ is SH and compounds of structure(III) in which L² is a leaving group.

The reaction between compounds of structure (IV) and compounds ofstructure (V) can be carried out under acidic conditions in a suitablesolvent at a temperature between ambient and reflux temperature of thesolvent used.

Suitably the reaction is carried out in polar solvents, for example,lower alkanols, dimethyl sulphoxide, acetone, dimethylformamide oracetonitrile, optionally in the presence of water. Preferably thereaction is carried out in ethanol.

Suitably the reaction is carried out in the presence of a strong acid,for example hydrobromic or hydrochloric acid. Preferably the reaction iscarried out in the presence of hydrochloric acid.

Preferably the reaction is carried out at the reflux temperature of thesolvent.

The reaction between a compound of structure (VI) and a compound ofstructure (VII) can be carried out in an inert solvent at ambient orelevated temperature depending on the nature of groups M and Z. Suitablesolvents include those solvents usually employed for the reaction ofenolate ions with alkylating agents, for example, tetrahydrofuran,diethylether, benzene or toluene. Preferably, when M is lithium and Z ischlorine, the reaction is conducted in benzene at reflux temperature.

The reaction between a compound of structure (VIII) and a compound ofstructure (IX) can be carried out in an organic solvent, for example,tetrahydrofuran or diethylether, under conditions normally used fororganometallic reactions as will be well known to those skilled in theart.

The products of reactions (a) to (c) are compounds of structure (I) inwhich n is 0. These products can be oxidised to compounds of structure(I) in which n is 1 by reaction with an oxidising agent. Suitableoxidising agents include, for example, nitric acid, hydrogen peroxide,peracids, peresters, ozone, dinitrogen tetroxide, iodosobenzene,N-halosuccinamide, 1-chlorobenzotriazole, hypohalites, for examplesodium hypochlorite or t-butyl hypochlorite, diazabicylo [2,2,2]-octanebromine complex, sodium metaperiodate, selenium dioxide, manganesedioxide, chromic acid, ceric ammonium nitrate, bromine, chlorine, orsulphuryl chloride. Preferably the oxidising agent is m-chloroperbenzoicacid.

The oxidation reaction is carried out under conditions known in the artfor the oxidation of thiols to sulphoxides. Suitably, the reaction iscarried out in an inert solvent at a temperature of between -70° and theboiling point of the solvent used. Suitable solvents include aromatic orchlorinated hydrocarbons, for example benzene, toluene, dichloromethaneor chloroform, esters, for example ethyl acetate, or ethers, for exampledioxan. Preferably, the reaction is carried out in dichloromethane at atemperature of between -50° and +20° C.

The compounds of structure (I) are obtained either as the free base, orin the form of a salt depending on the choice of starting materials andreaction conditions. If the free compound is obtained it can beconverted into a salt by standard techniques well-known to those skilledin the art, for example by dissolving the compound in a suitable solventand adding the desired acid or base; alternatively, if a salt isobtained it can be converted into the free compound, again by standardtechniques, for example by treatment with an appropriate acid or base.

Racemic mixtures may be produced and can be separated by standardtechniques e.g. recrystallisation from optically active solvent or byhigh performance liquid affinity chromatography as described by S.Allenmark, B. Bomgren, H. Baren and P-O Lagerstrom in AnalyticalBiochemistry, 136, 293-7, 1984.

The intermediates of structure (IV) and the intermediate benzimidazolestructures (II), (VI) and (VIII) are known or can be prepared by methodsanalogous to those known in the art. For example compounds of structure(II) in which L¹ is SH can be prepared by reacting the correspondingcompounds of structure (IV) with carbon disulphide in the presence ifalkali metal hydroxides, or with potassium ethylxanthate (Org. Syn., 30,56) or thiophosgene. Compounds of structure (II) in which L¹ is aleaving group, for example halogen can be obtained from thecorresponding compounds of structure (II) in which L¹ is hydroxy bytreatment with for example, phosphorous oxychloride. The compounds ofstructure (II) in which L¹ is hydroxy can be prepared by reactingcompounds of structure (IV) with phosgene. Compounds of structure (IV)can be prepared by methods analogous to those described in EP No.127763A, DE No. 2848531, CA, 60, 13352h, 1964 and Liebigs Ann. Chem.,730, 16-30, 1969.

Compounds of structure (VI) can be prepared by methylation, oxidationand protection (i.e. introduction of the group R⁹) of compounds ofstructure (II) in which L¹ is SH.

Compounds of structures (III), (V), (VII) and (IX) are novel and providea further aspect of the invention. They can be prepared by methodsanalogous to those well known in the art, for example, compounds ofstructure (III) in which L² is a leaving group displaceable by mercaptanand R⁷ is NH₂ can be prepared from the corresponding compounds ofstructure (III) in which R⁷ is hydrogen, by:

(i) reaction of a compound of structure (III) in which R⁷ is hydrogenand L² is, for example, methoxy, with nitric acid and sulphuric acid togive a compound of structure (III) in which R⁷ is a nitro group.Reduction of the intermediate nitro derivative so formed, gives acompound of structure (III) in which R⁷ is NH₂ and L² is methoxy.Deprotection of the group L² with, for example, boron tribromide gives acompound of structure (III) in which L² is hydroxy. The hydroxy groupcan then be converted to other suitable groups L² using standardprocedures, for example, reaction with p-toluenesulphonyl chloride givesa compound of structure (III) in which L² is O-toluenesulphonyl; orreaction with thionyl chloride gives a compound of structure (III) inwhich L² is chlorine; or

(ii) reaction of a compound of structure (III) in which R⁷ is hydrogenand L² is, for example, methoxy with, for example, bromine to give acompound of structure (III) in which R⁷ is bromine. Reaction of theintermediate so formed with ammonia gives the required compound ofstructure (III) in which R⁷ is NH₂ and L² is methoxy. Reaction of thecompound of structure (III) so formed with, for example, borontribromide gives the corresponding compound of structure (III) in whichL² is hydroxy. The group L² can then be modified by standard procedures,for example, as described in (i) above.

Compounds of structure (III) in which R⁷ is hydrogen can themselves beprepared by methods analogous to those known in the art. For example, byreaction of a compound of structure (X) ##STR10## in which R⁸ ishalogen, for example chlorine or bromine, and L² is methoxy or hydroxy,with a suitable amine of structure R⁵ R⁶ NH in which R⁵ and R⁶ are asdescribed for structure (I).

Suitable conditions include heating in a suitable inert solvent, forexample tetrahydrofuran in the presence of an excess of amine.

Compounds of structure (X) can be prepared by methods well known tothose skilled in the art, for example by reaction of the correspondingcompounds in which R⁸ is hydroxy with, for example, phosphorusoxychloride to form a compound of structure (X) in which R⁸ is chlorine.

Compounds of structure (X) in which R⁸ is hydroxy can be prepared byreaction of an appropriately substituted amidine with an appropriatelysubstituted β-keto-ester. For example, reaction of methoxyacetamidinehydrochloride and ethyl formyl acetate sodium salt gives a compound ofstructure (X) in which X is nitrogen, Y is CH and L² is methoxy; andreaction of formamidine acetate and 3-keto-4-methoxybutyric acid ethylester gives a compound of structure (X) in which X is CH, Y is nitrogenand L² is methoxy.

Compounds of structure (III) in which L² is SH can be prepared fromcompounds of structure (III) in which L² is a leaving group, forexample, halogen by reaction with, for example NaSH.

Compounds of structure (V) can be prepared from the correspondingcompounds of structure (III); for example, compounds of structure (V) inwhich X¹ is CSCl can be prepared by reaction of a compound of structure(III) in which L² is SH with thiophosgene.

Compounds of structure (VII) can be prepared by methods analogous tothose described in Roszniki Chem., 35, 475, 1961.

The compounds of structure (I) and their pharmaceutically acceptablesalts inhibit exogenously and endogenously stimulated gastric acidsecretion and are useful in the treatment of gastro-intestinal diseasesin mammals, in particular humans. Such diseases include, for example,gastric and duodenal ulcers, and Zollinger-Ellison Syndrome.

Further, the compounds of structure (I) can be used in the treatment ofother disorders where a cytoprotective and/or anti-secretory effect isdesirable, for example, in patients with gastritis, NSAID inducedgastritis, gastritis associated with a history of chronic and excessivealcohol consumption, gastric ulcers, acute upper gastrointestinalbleeding, for the prophylaxis of upper gastrointestinal haemmorage inpatients at risk of the development of stress-related lesions of thegastric mucosa, and in the reduction of risk factors, for examplegastric acidity and volume associated with pulmonary aspiration.

It is believed that, after administration to mammals, compounds ofstructure (I) in which n is 0 exert their anti-secretory andcytoprotective activities after conversion into compounds of structure(I) in which n is 1.

Furthermore it is believed that compounds of structure (I) in which n is1, after administration to mammals, exert their anti-secretory activityafter transformation under acid conditions into another chemicallyreactive species. Active species so generated from compounds ofstructure (I) are within the scope of the present invention.

In therapeutic use, the compounds of the present invention are usuallyadministered in a standard pharmaceutical composition. The presentinvention therefore provides in a further aspect pharmaceuticalcompositions comprising a compound of structure (I) or apharmaceutically acceptable salt thereof and a pharmaceuticallyacceptable carrier.

Compounds of structure (I) and their pharmaceutically acceptable saltscan be administered in standard manner for example, orally,parenterally, rectally, transdermally, via inhalation or via buccaladministration.

The compounds of structure (I) and their pharmaceutically acceptablesalts which are active when given orally can be formulated as liquids,for example syrups, suspensions or emulsions, tablets, capsules andlozenges.

A liquid formulation will generally consist of a suspension or solutionof the compound or pharmaceutically acceptable salt in a suitable liquidcarrier(s) for example, ethanol, glycerine, non-aqueous solvent, forexample polyethylene glycol, oils, or water with a suspending agent,preservative, flavouring or colouring agent.

A composition in the form of a tablet can be prepared using any suitablepharmaceutical carrier(s) routinely used for preparing solidformulations. Examples of such carriers include magnesium stearate,starch, lactose, sucrose and cellulose.

A composition in the form of a capsule can be prepared using routineencapsulation procedures. For example, pellets containing the activeingredient can be prepared using standard carriers and then filled intoa hard gelatin capsule; alternatively, a dispersion or suspension can beprepared using any suitable pharmaceutical carrier(s), for exampleaqueous gums, celluloses, silicates or oils and the dispersion orsuspension then filled into a soft gelatin capsule.

Compounds of structure (I) in which n is 1 are susceptible todecomposition in acid media, and thus tablets and capsules containingsuch compounds are preferably provided with an enteric coating toprotect the compound from acid degradation in the stomach or capsulesused which are inherently acid resistant. Alternatively, the entericcoating can be provided by coating pellets containing the activeingredient before filling them into the hard gelatin capsule. Suitableenteric coating materials are those well known in the art of pharmacyand include for example shellac or anionic-film forming polymers such ascellulose acetate phthalate and hydroxypropylmethyl cellulose phthalateand the like, optionally in the presence of a plasticizer.

It will be apparent to those skilled in the art that other standardtechniques for enhancing the stability of such compounds can be used.The nature of such techniques will depend on the route of administrationand include, for example, the formation of stable complexes with, forexample β-cyclodextrin.

The compounds of structure (I) and their pharmaceutically acceptablesalts which are active when administered parenterally (i.e. by injectionor infusion) can be formulated as solutions or suspensions.

A composition for parenteral administration will generally consist of asolution or suspension of the active ingredient in a sterile aqueouscarrier or parenterally acceptable oil, for example polyethylene glycol,polyvinyl pyrrolidone, lecithin, arachis oil or sesame oil.Alternatively, the solution can be lyophilised and then reconstitutedwith a suitable solvent just prior to administration.

A typical suppository composition comprises a compound of formula (I) ora pharmaceutically acceptable salt thereof which is active whenadministered in this way, with a binding and/or lubricating agent suchas polymeric glycols, gelatins or cocoa butter or other low meltingvegetable or synthetic waxes or fats.

A typical transdermal formulation comprises a conventional aqueous ornon-aqueous vehicle, for example, a cream, ointment lotion or paste orin the form of a medicated plaster, patch or membrane.

A typical composition for inhalation comprises a solution, suspension oremulsion that may be administered in the form of an aerosol using aconventional propellant such as dichlorodifluoromethane ortrichlorofluoromethane.

Preferably the composition is in unit dose form. Each dosage unit fororal administration contains preferably from 1 to 250 mg (and forparenteral administration contains preferably from 1 to 150 mg) of acompound of the formula (I) or a pharmaceutically acceptable saltthereof calculated as the free base.

The present invention provides a method of inhibiting gastric acidsecretion which comprises administering to a mammal in need thereof aneffective amount of a compound of structure (I) or a pharmaceuticallyacceptable salt thereof.

The present invention also provides a method for the treatment ofgastro-intestinal diseases and other conditions caused or exacerbated bygastric acidity which comprises administering to a mammal in needthereof an effective amount of a compound of structure (I) or apharmaceutically acceptable salt thereof.

The daily dosage regimen for an adult patient may be, for example, anoral dose of between 1 mg and 500 mg, preferably between 1 mg and 250mg, or an intravenous, subcutaneous, or intramuscular dose of between 1mg and 500 mg, preferably between 1 mg and 150 mg, of the compound ofthe formula (I) or a pharmaceutically acceptable salt thereof calculatedas the free base, the compound being administered 1 to 4 times per day.Suitably the compounds will be administered for a period of continuoustherapy, for example for a week or more.

In addition, the compounds of the present invention can beco-administered with further active ingredients, such as antacids (forexample magnesium carbonate or hydroxide and aluminium hydroxide),non-steroidal anti-flammatory drugs (for example indomethacin, aspirinor naproxen), steroids, or nitrite scavengers (for example ascorbic acidor aminosulphonic acid), or other drugs used for treating gastriculcers, for example pirenzipine, prostanoids for example 16,16 dimethylPGE₂ or histamine H₂ -antagonists, for example cimetidine.

The following examples illustrate the invention. Temperatures arerecorded in degrees centigrade.

EXAMPLE 1 Preparation of5-Methoxy-2-(4-piperidino-2-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) A mixture of methoxyacetamidine hydrochloride (57 g) and ethylformyl acetate sodium salt (150.5 g) in water (670 ml) were stirred atroom temperature for 3 days. The volume was reduced and the solutionacidified, saturated with sodium chloride and extracted with chloroform.After drying (MgSO₄), the extracts were stripped to a solid which wastriturated with ether to give 2-methoxymethyl-4-pyrimidone (53.5 g) m.p.125°-7°.

(ii) A mixture of 2-methoxymethyl-4-pyrimidone (1.73 g) and phosphorusoxychloride (20 ml) were heated together under reflux for 30 minutes.The mixture was stripped, ice/water added and the pH raised to 14(NaOH). The solution was extracted with chloroform, the extracts dried(MgSO₄) and stripped to give 2-methoxymethyl-4-chloropyrimidine (1.72 g)as an oil which was used without further purification.

(iii) Piperidine (6.17 ml) in dichloromethane (40 ml) was added dropwiseto a solution of 2-methoxymethyl-4-chloropyrimidine (4.71 g) indichloromethane (40 ml). After standing overnight at room temperaturethe mixture was heated under reflux for 1 hour. After cooling thesolution was washed with water, dried and stripped. The residue waschromatographed (silica gel, CHCl₃) to give2-methoxymethyl-4-piperidinopyrimidine (4.49 g) as an oil.

(iv) Boron tribromide (6.1 ml) was added dropwise to a stirred solutionof 2-methoxymethyl-4-piperidinopyrimidine (3.35 g) in dichloromethane(60 ml) at 0°-5° under nitrogen. After a further 30 minutes the mixturewas poured onto ice, the pH raised to 13 (NaOH) and extracted withchloroform. The combined extracts were dried (K₂ CO₃) and the volumereduced. Ether was added to give 2-hydroxymethyl-4-piperidino-pyrimidine(2.78 g) as a crystalline solid, m.p. 92°-3°.

(v) Thionyl chloride (3.01 ml) was added dropwise to a stirred solutionof 2-hydroxymethyl-4-piperidinopyrimidine (2.66 g) in chloroform (20 ml)cooled in an ice/salt bath. The mixture was allowed to warm to roomtemperature and stirred for a further 2.5 hours. The solution was pouredonto ice, the pH raised to ca. 8 (NaOH), and extracted with chloroform.The extracts were dried and stripped to give2-chloromethyl-4-piperidino-pyrimidine (2.92 g) as an unstable oil whichwas used immediately.

(vi) A mixture of 2-chloromethyl-4-piperidinopyrimidine (2.89 g) and2-mercapto-5-methoxybenzimidazole (2.46 g) in ethanol (40 ml) and lNsodium hydroxide (15 ml) was stirred at room temperature for 16 hours.After stripping the residue was washed with water and recrystallisedfrom acetonitrile to give5-methoxy-2-(4-piperidino-2-pyrimidinylmethylthio)-(1H)-benzimidazole(3.5 g) m.p. 145°-147°.

EXAMPLE 2 Preparation of5-methoxy-2-(4-piperidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

A solution of m-chloroperbenzoic acid (1.69 g) in dichloromethane (25ml) was added to a stirred solution of5-methoxy-2-[4-piperidino-2-pyrimidinylmethylthio]-(1H) benzimidazole(3.48 g) in dichloromethane (75 ml) cooled to between -30° and -35°.After 1.5 hours at -20° a further quantity of m-chloroperbenzoic acid(0.34 g) was added. After a further 30 minutes ammonia was passedthrough the reaction mixture and the precipitated solid filtered off.The filtrate was washed with aqueous sodium carbonate, which was backwashed with chloroform. The combined organic phases were dried (K₂ CO₃)stripped and the residue purified by column chromatography (silica gel,2% MeOH-NH₃ /CHCl₃) to give5-methoxy-2-(4-piperidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole(3.28 g) as an oil.

EXAMPLE 3 Preparation of5-methoxy-2-(4-piperidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazoleCalcium Salt 2.5 H₂ O

5-Methoxy-2-(4-piperidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole(3.28 g) was partitioned between dichloromethane (20 ml), water (20 ml)and 1N sodium hydroxide (8.83 ml). The organic phase was separated offand the aqueous phase filtered and treated with a solution of calciumchloride (6H₂ O, 0.97 g) in water (10 ml). The precipitate was filteredoff and dried to give the title compound (1.89 g) m.p. 204°-6° (dec).

C₃₆ H₄₀ CaN₁₀ O₄ S₂.2.5H₂ O:

Found:C, 52.30; H, 5.43; N, 16.71; S, 7.71%:

Requires: C, 52.34; H, 5.19; N, 16.96; S, 7.76%.

EXAMPLE 4 Preparation of 5-methoxy-2-(4-morpholino-2-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) A solution of morpholine (12.67 g) and2-methoxymethyl-4-chloropyrimidine (7.69 g) in tetrahydrofuran (100 ml)was heated under reflux for 1 hour. On cooling, the mixture was treatedwith water (100 ml), the pH adjusted to 8 (conc HCl) and extracted withchloroform. After drying (K₂ CO₃) the extracts were stripped, and theresidue purified by chromatography (silica gel, CHCl₃ /methanol) to give2-methoxymethyl-4-morpholinopyrimidine (5.4 g) as an oil.

(ii) A solution of boron tribromide (9.02 ml) in dichloromethane (100ml) was added dropwise to a stirred solution of2-methoxymethyl-4-morpholinopyrimidine (4.99 g) in dichloromethane (50ml) at -25° under nitrogen. After 15 minutes the mixture was allowed towarm to 0°-5°, and left to stand for 2 hours at this temperature. Afterpouring onto ice, the pH was raised to 14 (NaOH), and the organic phaseseparated off. The aqueous phase was further extracted with chloroform,and the combined extracts dried (K₂ CO₃) and stripped. The residue wastriturated with ether to give 2-hydroxymethyl-4-morpholinopyrimidine(3.16 g) as a crystalline solid, m.p. 76°-8°.

(iii) Thionyl chloride (3.4 ml) was added dropwise to a stirred solutionof 2-hydroxymethyl-4-morpholinopyrimidine in chloroform (30 ml) cooledin an ice bath. The mixture was allowed to warm to room temperature andleft to stand for a further 1.5 hours. The solution was reduced to lowvolume, and ether added with stirring to give2-chloromethyl-4-morpholinopyrimidine hydrochloride (3.8 g) as acrystalline solid, m.p. 214°-6°.

(iv) 5N sodium hydroxide (6.42 ml) was added dropwise to a stirredmixture of 2-chloromethyl-4-morpholinopyrimidine hydrochloride (3.65 g)and 2-mercapto-5-methoxybenzimidazole (2.63 g). Stirring was continuedfor 1.5 hours and the mixture was allowed to stand for a further 16hours. After stripping, the solid residue was washed with water andrecrystallised from acetonitrile to give5-methoxy-2-(4-morpholino-2-pyrimidinylmethylthio)-(1H)-benzimidazole(4.09 g), m.p. 188°-92°.

EXAMPLE 5 Preparation of5-methoxy-2-(4-morpholino-2-pyrimidinyl-methylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(4-morpholino-2-pyrimidinylmethylthio)-(1H)-benzimidazole(3.53 g) for5-methoxy-2-(4-piperidino-2-pyrimidinylmethylthio)-(1H)-benzimidazoleand using corresponding molar proportions of the other reagents in themethod of Example 2 gave5-methoxy-2-(4-morpholino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole(2.58 g), m.p. 154-6 (dec), from acetonitrile.

C₁₇ H₁₉ N₅ O₃ S:

Found: C, 54,85; H, 5.11; N, 18.64; S, 8.61.

Requires: C, 54.68; H, 5.13; N, 18.76; S, 8.59.

EXAMPLE 6 Preparation of5-methoxy-2-(4-pyrrolidino-2-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) Substituting pyrrolidine (8.51 ml) for piperidine and usingcorresponding molar proportions of the other reagents in the method ofExample 1(iii), gave5-methoxy-2-(4-pyrrolidino-2-pyrimidinylmethylthio)-(1H)-benzimidazole(8.49 g) as an oil.

(ii) Substituting 2-methoxymethyl-4-pyrrolidinopyrimidine (8.31 g) for2-methoxymethyl-4-piperidinopyrimidine and using corresponding molarproportions of the other reagents in the method of Example 1(iv), gave2-hydroxymethyl-4-pyrrolidino-pyrimidine (6.72 g), m.p. 114°-6°, fromether.

(iii) Substituting 2-hydroxymethyl-4-pyrrolidinopyrimidine (3.0 g) for2-hydroxymethyl-4-morpholino pyrimidine and using corresponding molarproportions of the other reagents in the method of Example 4(iii), gave2-chloromethyl-4-pyrrolidino-pyrimidine hydrochloride (3.72 g), m.p.186°-9°.

(iv) Substituting 2-chloromethyl-4-pyrrolidinopyrimidine hydrochloride(3.61 g) for 2-chloromethyl-4-morpholino-pyrimidine hydrochloride andusing corresponding molar proportions of the other reagents in themethod of Example 4(iv), gave5-methoxy-2-(4-pyrrolidino-2-pyrimidinylmethylthio)-(1H)-benzimidazole(4.03 g), m.p. 199°-202°, from ethanol.

EXAMPLE 7 Preparation of5-methoxy-2-(4-pyrrolidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(4-pyrrolidino-2-pyrimidinyl-methylthio)-(1H)-benzimidazole(3.92 g) for5-methoxy-2-(4-piperidino-2-pyrimidinylmethylthio)-(1H)-benzimidazoleand using corresponding molar proportions of the other reagents in themethod of Example 2 gave5-methoxy-2-(4-pyrrolidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole(2.88 g), m.p. 175°-7° (dec) from acetonitrile.

C₁₇ H₁₉ N₅ O₂ S:

Found: C, 57.01; H, 5.35; N, 19.50; S, 9.08.

Requires: C, 57.12; H, 5.36; N, 19.59; S, 8.97.

EXAMPLE 8 Preparation of5-methoxy-2-(4-dimethylamino-2-pyrimidinyl-methylthio)-(1H)-benzimidazole

(i) A 33% w/w solution of dimethylamine in ethanol (45 ml) was addeddropwise to a stirred solution of 2-methoxymethyl-4-chloropyrimidine(7.54 g) in ethanol (100 ml), cooled over an ice bath. The mixture wasallowed to warm to room temperature, and left to stand for 16 hours.After stripping, the residue was treated with water (100 ml), andextracted with chloroform. The extracts were dried (K₂ CO₃) and strippedto give 2-methoxymethyl-4-dimethylaminopyrimidine (7.41 g) as an oil.

(ii) Substituting 2-methoxymethyl-4-dimethylaminopyrimidine (7.2 g) for2-methoxymethyl-4-piperidinopyrimidine and using corresponding molarproportions of the other reagents in the method of Example 1(iv), gave2-hydroxymethyl-4-dimethylaminopyrimidine (5.7 g), m.p. 83°-4°, fromether.

(iii) Substituting 2-hydroxymethyl-4-dimethylaminopyrimidine (5.55 g)for 2-hydroxymethyl-4-morpholinopyrimidine and using corresponding molarproportions of the other reagents in the method of Example 4(iii), gave2-chloromethyl-4-dimethylaminopyrimidine hydrochloride (7.39 g), m.p.204°-6° from ether.

(iv) Substituting 2-chloromethyl-4-dimethylaminopyrimidine hydrochloride(3.7 g) for 2-chloromethyl-4-morpholinopyrimidine hydrochloride andusing corresponding molar proportions of the other reagents in themethod of Example 4(iv), gave5-methoxy-2-(4-dimethylamino-2-pyrimidinylmethylthio)-(1H)-benzimidazole(4.41 g), m.p. 182°-3°, from ethanol.

EXAMPLE 9 Preparation of5-methoxy-2-(4-dimethylamino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(4-dimethylamino-2-pyrimidinylmethylthio)-(1H)-benzimidazole(4.25 g) for5-methoxy-2-(4-piperidino-2-pyrimidinylmethylthio)-(1H)-benzimidazoleand using corresponding molar proportions of the other reagents in themethod of Example 2 gave5-methoxy-2-(4-dimethylamino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole(2.67 g), m.p. 138°-40° (dec) from acetonitrile.

C₁₅ H₁₇ N₅ O₂ S:

Found: C, 54,46; H, 4.97; N, 21.07; S, 9.56.

Requires: C, 54.36; H, 5.17; N, 21.13; S, 9.68.

EXAMPLE 10 Preparation of5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) 2-Methyl-3-keto-4-methoxybutyric acid ethyl ester (60 g) andformamidine acetate (39.06 g) were dissolved in methanol (150 ml) andtreated, under nitrogen, with a sodium methoxide solution, prepared fromsodium (17.42 g) and methanol (225 ml). The mixture was stirred at 50°for 23 hours, stripped, water added and the pH lowered to 7 (HCl). Thesolution was extracted with chloroform, extracts dried (MgSO₄) andstripped to a residue, which was triturated with diethyl ether to give4-methoxymethyl-5-methyl-6-hydroxypyrimidine, 38.72 g, m.p. 139°-140°.

(ii) 4-Methoxymethyl-5-methyl-6-hydroxypyrimidine (38.40 g) was stirredwith phosphorus oxychloride (275 ml) at room temperature for 24 hours.The mixture was stripped, ice/water added and the pH raised to 11.5(NaOH). The solution was extracted with chloroform, extracts dried(MgSO₄) and stripped to give4-methoxymethyl-5-methyl-6-chloropyrimidine, 38.23 g, as an oil, whichsolidified on cooling to 5° (m.p. 37°-38°). It was used without furtherpurification.

(iii) Piperidine (15 ml) in tetrahydrofuran (40 ml) was added dropwiseto a solution of 4-methoxymethyl-5-methyl-6-chloropyrimidine (5 g) intetrahydrofuran (40 ml). The mixture was heated under reflux for 7 hoursand then allowed to stand overnight at room temperature. It wasfiltered, stripped, and water added to the residual oil. The pH waslowered to 7.5 (HCl) and extracted with chloroform. Extracts were dried(K₂ CO₃) and stripped to give4-methoxymethyl-5-methyl-6-piperidinopyrimidine, 6.08 g, as an oil,which solidified on cooling to 5° (m.p. 45°-47°). It was used withoutfurther purification.

(iv) Boron tribromide (8.9 ml) in dichloromethane (25 ml) was addeddropwise, under nitrogen, to a stirred solution of4-methoxymethyl-5-methyl-6-piperidinopyrimidine (5 g) in dichloromethane(100 ml) at 0°-5°. After a further 2 hours the mixture was poured ontoice, the pH raised to 13 (NaOH) and extracted with chloroform. Extractswere dried (K₂ CO₃) and stripped to a residue, which was triturated withdiethyl ether to give 4-hydroxymethyl-5-methyl-6-piperidinopyrimidine,3.80 g, as a crystalline solid, m.p. 79°-81°.

(v) Thionyl chloride (4.5 ml) in chloroform (30 ml) was added dropwiseto a stirred solution of 4-hydroxymethyl-5-methyl-6-piperidinopyrimidine(4.24 g) in chloroform (30 ml) cooled in an ice-salt bath. The mixturewas allowed to warm to room temperature and stirred for a further 22hours. The solution was stripped to a residual glass which wastriturated with diethyl ether to give4-chloromethyl-5-methyl-6-piperidino-pyrimidine hydrochloride, 5.24 g,m.p. 182°-184°.

(vi) A mixture of 4-chloromethyl-5-methyl-6-piperidino pyrimidinehydrochloride (4.63 g) and 2-mercapto-5-methoxybenzimidazole (3.18 g) inethanol (180 ml) were heated at 50° for 5 hours. The solution wasstripped to a residual glass, to which water was added, the pH raised to13 (NaOH), and extracted with chloroform. Extracts were dried (K₂ CO₃)and stripped to a residual glass which crystallised from ethyl acetateto give5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole,5.67 g, m.p. 94°-96°.

EXAMPLE 11 Preparation of5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

A solution of m-chloroperbenzoic acid (2.16 g) in dichloromethane (40ml) was added to a stirred solution of5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole(4.0 g) in dichloromethane (110 ml) cooled to between -40° and -50°.After a further hour at -40°, ammonia was passed through the reactionmixture and the precipitated solid filtered off. The filtrate wasstripped, and the residual glass triturated with acetonitrile to give5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole2.66 g, m.p. 87°-89°.

C₁₉ H₂₃ H₅ O₂ S 0.5H₂ O:

Found: C, 58.22; H, 5.87; N, 17.78; S, 8.43.

Requires: C, 57.93; H, 6.12; N, 17.78; S, 8.14.

EXAMPLE 12 Preparation of5-methoxy-2-(5-methyl-6-pyrrolidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) Substituting pyrrolidine (12.20 ml) for piperidine, 1,4-dioxan assolvent for tetrahydrofuran, and using corresponding molar proportionsof the other reagents, in the method of Example 10(iii), gave4-methoxymethyl-5-methyl-6-pyrrolidinopyrimidine, 5.52 g, as an oil. Itwas used without further purification.

(ii) Substituting 4-methoxymethyl-5-methyl-6-pyrrolidino pyrimidine (5.4g) for 4-methoxymethyl-5-methyl-6-piperidinopyrimidine and usingcorresponding molar proportions of the other reagents in the method ofExample 10(iv), gave 4-hydroxymethyl-5-methyl-6-pyrrolidinopyrimidine,4.11 g, m.p. 112°-114°, from diethyl ether.

(iii) Substituting 4-hydroxymethyl-5-methyl-6-pyrrolidino pyrimidine(3.90 g) for 4-hydroxymethyl-5-methyl-6-piperidinopyrimidine and usingcorresponding molar proportions of the other reagents in the method ofExample 10(v), gave 4-chloromethyl-5-methyl-6-pyrrolidinopyrimidinehydrochloride, 4.88 g, m.p. 173°-175°.

(iv) Substituting 4-chloromethyl-5-methyl-6-pyrrolidinopyrimidinehydrochloride (4.80 g) for 4-chloromethyl-5-methyl-6-piperidinopyrimidine hydrochloride in the method of Example 10(vi) andusing corresponding molar proportions of other reagents, gave5-methoxy-2-(5-methyl-6-pyrrolidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole,5.78 g, m.p. 104°-106°, from acetonitrile.

EXAMPLE 13 Preparation of5-methoxy-2-(5-methyl-6-pyrrolidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(5-methyl-6-pyrrolidino-4-pyrimidinylmethylthio)-(1H)-benzimidazolefor5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)benzimidazoleand using corresponding molar proportions of other reagents in themethod of Example 11 gave5-methoxy-2-(5-methyl-6-pyrrolidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole3.33 g, m.p. 144°-146° (dec), from acetonitrile.

C₁₈ H₂₁ N₅ O₂ S:

Found: C, 58.14; H, 5.70; N, 18.66; S, 8.57.

Require: C, 58.20; H, 5.70; N, 8.85; S, 8.63.

EXAMPLE 14 Preparation of5-methoxy-2-(5-methyl-6-morpholino-4-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) Substituting morpholine (12.9 ml) for piperidine, 1,4-dioxan assolvent for tetrahydrofuran, and using corresponding molar proportionsof the other reagents, in the method of Example 10(iii), gave4-methoxymethyl-5-methyl-6-morpholinopyrimidine, 5.81 g, as an oil. Itwas used without further purification.

(ii) Substituting 4-methoxymethyl-5-methyl-6-morpholinopyrimidine, (5.77g), for 4-methoxymethyl-5-methyl-6-piperidinopyrimidine and usingcorresponding molar proportions of the other reagents in the method ofExample 10(iv), gave 4-hydroxymethyl-5-methyl-6-morpholinopyrimidine,3.46 g, m.p. 66°-68°, from petroleum ether (40/60).

(iii) Substituting 4-hydroxymethyl-5-methyl-6-morpholinopyrimidine (3.35g) for 4-hydroxymethyl-5-methyl-6-piperidinopyrimidine and usingcorresponding molar proportions of the other reagents in the method ofExample 10(v) gave 4-chloromethyl-5-methyl-6-morpholinopyrimidinehydrochloride, 4.22 g, m.p. 188°-190° (dec), from diethyl ether.

(iv) Substituting 4-chloromethyl-5-methyl-6-morpholinopyrimidinehydrochloride (4.17 g) for4-chloromethyl-5-methyl-6-piperidinopyrimidine hydrochloride and usingcorresponding molar proportions of the other reagents in the method ofExample 10(vi) gave5-methoxy-2-(5-methyl-6-morpholino-4-pyrimidinylmethylthio)-(1H)-benzimidazole,4.51 g, m.p. 129°-131°, from ethyl acetate.

EXAMPLE 15 Preparation of5-methoxy-2-(5-methyl-6-morpholino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(5-methyl-6-morpholino-4-pyrimidinylmethylthio)-(1H)-benzimidazolefor5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)benzimidazoleand using corresponding molar proportions of other reagents in themethod of Example 11 gave5-methoxy-2-(5-methyl-6-morpholino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole,2.67 g, m.p. 176°-178° (dec), from acetonitrile.

C₁₈ H₂₁ N₅ O₃ S:

Found: C, 55.74; H, 5.40; N, 17.96; S, 8.17.

Requires: C, 55.80; H, 5.46; N, 18.08; S, 8.28.

EXAMPLE 16 Preparation of5-methoxy-2-(5-methyl-6-dimethylamino-4-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) Substituting 4-methoxymethyl-5-methyl-6-chloropyrimidine (5.0 g) for2-methoxymethyl-4- chloropyrimine, and using corresponding molarproportions of the other reagents, in the method of Example 8(i), gave4-methoxymethyl-5-methyl-6-dimethylaminopyrimidine, 4.77 g, as an oil.It was used without further purification.

(ii) Substituting 4-methoxymethyl-5-methyl-6-dimethylaminopyrimidine(4.7 g) for 4-methoxymethyl-5-methyl-6-piperidinopyrimidine and usingcorresponding molar proportions of the other reagents in the method ofExample 10(iv), gave 4-hydroxymethyl-5-methyl-6-dimethylaminopyrimidine,3.52 g, m.p. 46°-48°, from petroleum ether (40-60).

(iii) Substituting 4-hydroxymethyl-5-methyl-6-dimethylaminopyrimidine(3.35 g) for 4-hydroxymethyl-5-methyl-6-piperidinopyrimidine and usingcorresponding molar proportions of the other reagents in the method ofExample 10(v), gave 4-chloromethyl-5-methyl-6-dimethylaminopyrimidinehydrochloride, 4.30 g, m.p. 176°-178°, from diethyl ether.

(iv) Substituting 4-chloromethyl-5-methyl-6-dimethylaminopyrimidinehydrochloride (4.20 g) for4-chloromethyl-5-methyl-6-piperidinopyrimidine hydrochloride and usingcorresponding molar proportions of the other reagents in the method ofExample 10, gave, after chromatography (silica gel, CHCl₃ /MeOH),5-methoxy-2-(5-methyl-6-dimethylamino-4-pyrimidinylmethylthio)-(1H)-benzimidazole,5.28 g, as a glass.

EXAMPLE 17 Preparation of5-methoxy-2-(5-methyl-6-dimethylamino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(5-methyl-6-dimethylamino-4-pyrimidinylmethylthio)-(1H)-benzimidazole(3.86 g) for5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazoleand using corresponding molar proportions of other reagents in themethod of Example 11, gave5-methoxy-2-(5-methyl-6-dimethylamino-4-pyrimidinyl-methylsulphinyl)-(1H)-benzimidazole,3.36 g, m.p. 141°-143° (dec), from acetonitrile.

C₁₆ H₁₉ N₅ O₂ S:

Found: C, 55.43; H, 5.64; N, 20.14; S, 9.25.

Requires: C, 55,63; H, 5.54; N, 20.27; S, 9.28.

EXAMPLE 18 Preparation of5-methoxy-2-(6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) Substituting 3-keto-4-methoxybutyric acid ethyl ester (35.75 g) for2-methyl-3-keto-4-methoxybutyric acid ethyl ester and usingcorresponding molar proportions of the other reagents in the method ofExample 10(i), gave 4-methoxymethyl-6-hydroxypyrimidine, 13.35 g, m.p.159°-161°, from diethyl ether.

(ii) Substituting 4-methoxymethyl-6-hydroxypyrimidine (15.40 g) for4-methoxymethyl-5-methyl-6-hydroxypyrimidine and using correspondingmolar proportions of the other reagents in the method of Example 10(ii),gave 4-methoxymethyl-6-chloropyrimidine, 16.77 g, m.p. 34°-36°. It wasused without further purification.

(iii) Substituting 4-methoxymethyl-6-chloropyrimidine (4.0 g) for4-methoxymethyl-5-methyl-6-chloropyrimidine and using correspondingmolar proportions of the other reagents in the method of Example 10(iii)gave 4-methoxymethyl-6-piperidino-pyrimidine, 4,88 g, as an oil. It wasused without further purification.

(iv) Substituting 4-methoxymethyl-6-piperidinopyrimidine (4.70 g) for4-methoxymethyl-5-methyl-6-piperidinopyrimidine and using correspondingmolar proportions of the other reagents in the method of Example 10(iv)gave 4-hydroxymethyl-6-piperidinopyrimidine, 3.67 g, m.p. 70°-72°, fromdiethyl ether.

(v) Substituting 4-hydroxymethyl-6-piperidinopyrimidine (3.56 g) for4-hydroxymethyl-5-methyl-6-piperidinopyrimidine and using correspondingmolar proportions of the other reagents in the method of Example 10(v)gave 4-chloromethyl-6-piperidinopyrimidine hydrochloride, 4.55 g, m.p.187°-189°, from diethyl ether.

(vi) Substituting 4-chloromethyl-6-piperidinopyrimidine hydrochloride(4.47 g) for 4-chloromethyl-5-methyl-6-piperidinopyrimidinehydrochloride and using corresponding molar proportions of the otherreagents in the method of Example 10(vi) gave, after chromatography(silica gel, CHCl₃ /MeOH),5-methoxy-2-(6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole,5.72 g, as a glass.

EXAMPLE 19 Preparation of5-methoxy-2-(6-piperidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole(4.12 g) for5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazoleand using corresponding molar proportions of other reagents in themethod of Example 2, gave5-methoxy-2-(6-piperidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole,2.44 g, m.p. 98°-101°, from ethyl acetate.

C₁₈ H₂₁ N₅ O₂ S 0.33 EtOAc 0.18H₂ O:

Found: C, 57.44; H, 5.93; N, 17.29; S, 7.90.

Requires: C, 57,47; H, 5.99; N, 17.36; S, 7.95.

EXAMPLE 20 Preparation of5-methoxy-2-(6-pyrrolidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) Substituting pyrrolidine (10.4 ml) for piperidine and usingcorresponding molar proportions of the other reagents in the method ofExample 18(iii), gave 4-methoxymethyl-6-pyrrolidino pyrimidine, 4.65 g,as an oil. It was used without further purification.

(ii) Substituting 4-methoxymethyl-6-pyrrolidinopyrimidine (4.60 g) for4-methoxymethyl-5-methyl-6-piperidinopyrimidine and using correspondingmolar proportions of the other reagents in the method of Example 10(iv),gave 4-hydroxymethyl-6-pyrrolidinopyrimidine, 3.84 g, m.p. 136°-139°,from diethyl ether.

(iii) Substituting 4-hydroxymethyl-6-pyrrolidinopyrimidine for4-hydroxymethyl-5-methyl-6-piperidinopyrimidine and using correspondingmolar proportions of the other reagents in the method of Example 10(v),gave 4-chloromethyl-6-pyrrolidinopyrimidine hydrochloride, 4.66 g, m.p.180°-182° (dec), from diethyl ether.

(iv) Substituting 4-chloromethyl-6-pyrrolidinopyrimidine hydrochloridefor 4-chloromethyl-5-methyl-6-piperidinopyrimidine hydrochloride andusing corresponding molar proportions of the other reagents in themethod of Example 10(vi), gave5-methoxy-2-(6-pyrrolidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole,6.41 g, as a glass.

EXAMPLE 21 Preparation of5-methoxy-2-(6-pyrrolidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(6-pyrrolidino-4-pyrimidinylmethylthio)-(1H)-benzimidazole(4.0 g) for5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazoleand using corresponding molar proportions of other reagents in themethod of Example 11, gave5-methoxy-2-(6-pyrrolidino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole,2.79 g, m.p. 95°-97° (dec), from acetonitrile.

C₁₇ H₁₉ N₅ O₂ S 0.04CH₂ CL₂ 0.67H₂ O:

Found: C, 55.01; H, 5.68; N, 18.72; S, 8.54.

Requires: C, 54.85; H, 5.52; N, 18.78; S, 8.59.

EXAMPLE 22 Preparation of5-methoxy-2-(6-dimethylamino-4-pyrimidinylmethylthio)-(1H)-benzimidazole

(i) Substituting 4-methoxymethyl-6-chloropyrimidine (4.0 g) for2-methoxymethyl-4-chloropyrimidine, and using corresponding molarproportions of the other reagents, in the method of Example 8(i), gave4-methoxymethyl-6-dimethylaminopyrimidine, 4.1 g, as a low meltingsolid, m.p. 42°-44°. It was used without further purification.

(ii) Substituting 4-methoxymethyl-6-dimethylaminopyrimidine (4.06 g) for4-methoxymethyl-5-methyl-6-piperidinopyrimidine and using correspondingmolar proportions of the other reagents in the method of Example 10(iv),gave 4-hydroxymethyl-6-dimethylaminopyrimidine, 3.05 g, m.p. 137°-139°,from diethyl ether.

(iii) Substituting 4-hydroxymethyl-6-dimethylaminopyrimidine (2.95 g)for 4-hydroxymethyl-5-methyl-6-piperidinopyrimidine and usingcorresponding molar proportions of the other reagents in the method ofExample 10(v), gave 4-chloromethyl-6-dimethylaminopyrimidinehydrochloride, 3.97 g, m.p. 225°-226° from diethyl ether.

(iv) Substituting 4-chloromethyl-6-dimethylaminopyrimidine hydrochloride(3.90 g) for 4-chloromethyl-5-methyl-6-piperidinopyrimidinehydrochloride and using corresponding molar proportions of the otherreagents in the method of Example 10(vi), gave5-methoxy-2-(6-dimethylamino-4-pyrimidinylmethylthio)-(1H)-benzimidazole,5.80 g, as a glass.

EXAMPLE 23 Preparation of5-methoxy-2-(6-dimethylamino-4-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole

Substituting5-methoxy-2-(6-dimethylamino-4-pyrimidinylmethylthio)-(1H)-benzimidazole(4.0 g) for5-methoxy-2-(5-methyl-6-piperidino-4-pyrimidinylmethylthio)-(1H)-benzimidazoleand using corresponding molar proportions of other reagents in themethod of Example 11, gave5-methoxy-2-(6-dimethylamino-4-pyrimidinylmethyl-sulphinyl)-(1H)-benzimidazole,3.06 g, m.p. 104°-106°, from acetonitrile.

C₁₅ H₁₇ N₅ O₂ S 0.23 CH₃ CN:

Found: C, 54.45; H, 5.33; N, 21.51; S, 9.23.

Requires: C, 54,48; H, 5.24; N, 21.50; S, 9.41.

EXAMPLE A

A tablet for oral administration is prepared by combining

    ______________________________________                                                         Mg/Tablet                                                    ______________________________________                                        Compound of structure (I)                                                                        100                                                        Mannitol           153                                                        Starch             33                                                         polyvinylpyrrolidone                                                                             12                                                         microcrystalline cellulose                                                                       30                                                         magnesium stearate 2                                                                             330        mg                                              ______________________________________                                    

into a 9 mm tablet. If the active ingredient is a compound of structure(I) in which n is 1 then the tablet is provided with an enteric coating.

EXAMPLE B

A pellet formulation for oral administration may be prepared byformulating the following into pellets by standard techniques

    ______________________________________                                                           % w:w                                                      ______________________________________                                        Compound of structure (I)                                                                          80                                                       microcrystalline cellulose                                                                         10                                                       sodium carboxymethylcellulose                                                                       2                                                       lactose               8                                                       ______________________________________                                    

If the active ingredient is a compound of structure (I) in which n is 1,the pellets are first enteric coated before being filled into hardgelatin capsules.

EXAMPLE C

An injection for parenteral administration is prepared by combining

    ______________________________________                                                          % w:w                                                       ______________________________________                                        Compound of example 1                                                                             1-5                                                       polyethylene glycol 40                                                        ethanol             10                                                        water for injection EP to                                                                         100                                                       ______________________________________                                    

The solution is then sterilised by an appropriate method and sealed into2 ml and 5 ml ampoules and vials.

EXAMPLE D

A reconstitutable lyophilisate for parenteral administration is preparedfrom:

    ______________________________________                                                           % w:w                                                      ______________________________________                                        Compound of structure (I) as a salt                                                                1-5                                                      Mannitol             3                                                        NaCl                 sufficient to make                                                            reconstituted                                                                 solution isotonic                                        water to             100                                                      ______________________________________                                    

The solution is sterilised by an appropriate method, 5 ml portionsdispensed into 15 ml vials and the solution lyophilised. Thelyophilisate can be reconstituted with a suitable carrier, for examplewater, a buffered solution or a co-solvent mixture.

Biological Data

Inhibition of gastric acid secretion is demonstrated by the followingtest procedures:

A. K⁺ Stimulated ATPase Activity

The effects of a single high concentration (1 mM) of a compound ofstructure (I) on H⁺ -K⁺ -ATPase were determined at pH 6.1 and pH 7.4.Preferred compounds of structure (I) were also tested over a range ofconcentrations to determine IC₅₀ values at pH 6.1 and 7.4.

(i) Preparation of Lyophilised Gastric Vesicles (H⁺ -K⁺ -ATPase)

H⁺ -K⁺ -ATPase was prepared from the lyophilised gastric vesicles of pigfundic mucosa after the method of Saccomani et. al. (Biochem andBiophys. Acta., 465, 311, 1977).

(ii) K⁺ Stimulated ATPase Activity

Compounds of structure (I) were pre-incubated with H⁺ -K⁺ -ATPasepreparation 30 μg protein/ml from (i) in 10 mM Pipes/Tris buffer pH 6.1and pH 7.4.

After 30 minutes at 37° the pre-incubation was diluted 5-fold with assaybuffer to start the ATPase reaction. The conditions in the assay are 100mM Pipes/Tris, 2 mM MgCl₂, 10 mM KCl, 5 μg/ml nigericin, 2 mM Na ATP, pH7.0. After an incubation at 37° for 15 minutes the inorganic phosphatereleased was determined by the method of Yoda & Hokin (Biochem. Biophys.Res. Com. 40, 880, 1970). Nigericin was dissolved in methanol, which atthe final concentration of 0.5%, did not affect the enzyme activity.

The effect of the same concentration of compound of structure (I)(pre-incubated with H⁺ -K⁺ -ATPase preparation at pH 7.4 as describedabove) on the recovery of 100 nmole of inorganic phosphate was alsodetermined.

Compounds of structure (I) were initially dissolved in dimethylsulphoxide, polyethylene glycol (Type 400) or Pipes/Tris buffer. None ofthese solvents affects K⁺ -ATPase activity at the concentrations used.

(iii) Results

The compound of Example 3 was found to inhibit potassium stimulated H⁺-K⁺ ATPase at pH6.1 and 7.4.

B. Aminopyrine (AP) accumulation in intact gastric glands

The effect of a single concentration (100 μm) of a compound of structure(I) on dibutyryl cAMP stimulated AP metabolism in rabbit intact gastricglands was determined. Preferred compounds of structure (I) were testedover a range of concentrations to determine the IC₅₀ value.

(i) Preparation of intact gastric glands.

Intact gastric glands were prepared from New Zealand white rabbits bythe method of Berghindh et al. (Acta. Physio. Scand. 96, 150, 1976).Gastric mucosal scrapings were digested at 37° C. for 45-60 min. withCollagenase (100 U, Type 1, Sigma), and glands harvested by coarsefiltration and sedimentation.

(ii) AP accumulation

Test compound was incubated with glands and 300 μM dibutyryl cAMP for 30minutes at 37° C. Incubating medium contained 132.5 mM NaCl, 5.4 mM KCl,1.0 mM NaH₂ PO₄, 5.0 mM Na₂ HPO₄, 1.2 mM MgSO₄, 1.0 mM CaCl₂, 11.1 mMglucose, 2.0 mg/ml rabbit albumin, 10 μg/ml phenol red, approximately0.3 μM[¹⁴ C] aminopyrine (110 mCi/mmole), pH 7.4.

After incubation, glands were centrifuged and the supernatant removed.The glands were dried, weighed and dissolved in NaOH. The distributionof radioactivity between the supernatant and glands is then used tocalculate the AP ratio after the method of Berglindh et al. (Acta.Physiol. Scand. 97, 401, 1976).

The IC₅₀ value is the amount of compound required to inhibit thestimulated accumulation of aminopyrine by 50%.

(iii) Results

    ______________________________________                                        Compound of Example                                                                              IC.sub.50 (μM)                                          ______________________________________                                         3                 16.00                                                       7                 2.44                                                        9                 1.20                                                       11                 6.15                                                       13                 0.32                                                       15                 5.00                                                       17                 3.33                                                       19                 2.64                                                       ______________________________________                                    

C. Rat: Lumen perfused stomach (histamine stimulated gastric acidsecretion).

Using a modification of the procedure described by Ghosh and Schild (Br.J. Pharmacology, 13, 54, 1958), ED₅₀ values after either intraduodenal(i.d) or intravenous (i.v) administration were obtained as follows:

    ______________________________________                                                         Route of    ED.sub.50                                        Compound of Example                                                                            Administration                                                                            μmol/kg                                       ______________________________________                                        3                i.v.        1.4                                              9                i.d.        2.4                                              13               i.d.        2.8                                              ______________________________________                                    

No overt signs of toxicity were observed in any of the foregoing tests.

What is claimed is:
 1. A compound of structure (I) ##STR11## in which R¹and R⁴ are the same or different and are each hydrogen, C₁₋₆ alkyl,halogen, trifluoromethyl, C₁₋₆ alkoxy, C₁₋₆ alkanoyl or C₁₋₆alkoxycarbonyl, RCF₂ O, an ethoxy group substituted by 3 to 5 fluorineatoms; R² and R³ together form a group --O(CR₂)_(m) O-- where m is 1 or2, and each group R is hydrogen or fluorine;n is 0 or 1; R⁵ and R⁶ arethe same or different and are each hydrogen, C₁₋₆ alkyl or C₃₋₆cycloalkyl, or R⁵ and R⁶ together with the nitrogen atom to which theyare attached form an azetidino, pyrrolidino, piperidino, piperazino,N-C₁₋₄ alkylpiperazino or morpholino group; and one of X and Y is anitrogen atom, and the other is a group CR⁷ where R⁷ is hydrogen, C₁₋₄alkyl or NH₂,or a pharmaceutically acceptable salt thereof.
 2. Acompound as claimed in claim 1 in which n is
 1. 3. A compound as claimedin claim 1 in which R⁵ and R⁶ together with the nitrogen claim to whichthey are attached form a pyrrolidino, piperidino, piperazino, NC₁₋₄alkyl piperazino, or morpholino group.
 4. A pharmaceutical compositioncomprising a compound as claimed in claim 1 in association with apharmaceutically acceptable carrier.
 5. A pharmaceutical compositioncomprising a compound as claimed in claim 2, in association with apharmaceutically acceptable carrier.
 6. A pharmaceutical composition asclaimed in claim 5, in a form suitable for oral administration.
 7. Apharmaceutical composition as claimed in claim 6, provided with anenteric coating.
 8. A pharmaceutical composition as claimed in claim 4in a form suitable for intravenous administration.
 9. A method ofinhibiting gastric acid secretion which comprises administering to amammal in need thereof an effective amount of a compound as claimed inclaim
 1. 10. A method of treatment of gastrointerstinal diseases andother conditions caused or exacerbated by gastric acidity whichcomprises administering to a mammal in need thereof an effective amountof a compound as claimed in claim 1.